Device for suspension and placement of the load in a distributive jib tower crane

ABSTRACT

A tower crane with a horizontal distributive jib is traversed by a carriage bearing hoist cables with terminal swivels from which hangs a crossbar. The crossbar carries a load-bearing hook. The hoist cables pass over guide pulleys on the carriage in opposite directions via a plurality of further pulleys to respective drums synchronized winches. The further pulleys include two mounted on a block which moves horizontally in a direction opposite to that of the carriage so as to compensate for the changes in length of the hoist cables and hence to keep the load at a constant level. The tendency of the hoist cables and crossbar to twist is thereby obviated.

United States Patent DEVICE FOR SUSPENSION AND DISPLACEMENT OF THE LOADIN A DISTRIBUTIVE JIB TOWER CRANE 7 Claims, 3 Drawing Figs.

US. Cl 212/63, 212/76, 212/81, 212/20, 212/27 Int. Cl B66c 23/02FieldofSearch, 212/19, 20,

Primary Examiner-Harvey C. l'lomsby Att0rney-Waters, Roditi, Schwartz &Nissen ABSTRACT: A tower crane with a horizontal distributive jib istraversed by a carriage bearing hoist cables with terminal swivels fromwhich hangs a crossbar. The crossbar carries a load-bearing hook. Thehoist cables pass over guide pulleys on the carriage in oppositedirections via a plurality of further pulleys to respective drumssynchronized winches. The further pulleys include two mounted on a blockwhich moves horizontally in a direction opposite to that of the carriageso as to compensate for the changes in length of the hoist cables andhence to keep the load at a constant level. The tendency of the hoistcables and crossbar to twist is thereby obviated.

DEVICE FOR SUSPENSION AND DISPLACEMENT OF THE LOAD IN A DISTRIBUTIVE JIBTOWER CRANE This invention relates to a device for the suspension anddisplacement of the load, applicable to tower cranes with a horizontaldistributive jib, and more particularly to those in which theload-bearing carriage does not bear the hoisting winch and serves onlyas movable starting point for the vertical cables which support thisload.

The invention will be more clearly understood from the followingdescription with reference to the accompanying diagrammatic drawings inwhich:

FIG. 1 shows the usual arrangement used in the case of these towercranes with a distributive jib;

FIG. 2 shows a second conventional arrangement based on the sameprinciple as that of FIG. 1; and

FIG. 3 shows an embodiment of the device according to the invention.

In FIG. 1, 1 designates the tower of a crane, 2 its distributive jib, 3the turning hook from which the load is suspended, and 4 theload-bearing carriage. The cables, respectively 5 for displacement ofthe load and 6 for displacement of the carriage, are independent and arecontrolled by two independent winches, respectively 7 and& The cable 6for displacement of the carriage fonns a closed loop of which thedisplacement movement draws the carriage 4 on the rolling trackgenerally constituted by the lower member of the jib. During thisdisplacement of the carriage 4, one of the strands of the cable 5 forsuspension of the load ascends, while the other descends by the sameamount, which enables the load to dwell at a constant height.

In FIG. 2 which shows a system for suspension and for displacement basedon the same principle as that of FIG. I, the suspension block 9comprises five pulleys; the load per strand hence becomes a quarter ofthe total load, and no longer half, as in the case of FIG. 1.

In the case of the arrangement shown in FIG. 1 or that shown in FIG. 2,the cable 5 being a twisted cable and being subject to a tractionthrough the load suspended at the hook, has a tendency to be untwisted,by the very reason of the dissymmetry of its internal construction. Thecouple which results therefrom is transmitted to the attachments at theend of the cable and to the block cheeks on which it is wound. This iswithout effect when the attachments and the pulleys are rigidly fixed;but it is not the same for the hanging part of the equipment. Theassembly: block, crossbar and hook being in fact subject to the sum ofthe untwisting couples of the strands of the cable, pivots around avertical axis, which has the effect of bringing together the suspensionstrands into a single twisted bundle. There results a troublesomephenomenon in working, and a source of wear and of risk of accident dueto the untwisting of the cable.

To avoid these disadvantages, at least partially, various solutions havebeen proposed and adopted, especially for example the use of so-calledantigyratory cables, of which the structure enables reduction of thetendency to untwist under load. Another solution consists of spreadingout or spacing to a maximum the various suspension strands, that is tosay to give the maximal dimension to the space a of FIGS. 1 and 2, so asto create a restoring couple which stabilizes the orientation of thecrossbar to an angle sufficiently reduced not to be troublesome. Yetanother solution consists of attaching the fixed point of the cable 5 ona swivel 10, as shown in FIG. 1, which swivel can turn freely so as toenable the cable to find its equilibrium in being untwisted withoutrestraint. This swivel is however only effective for the part of thecable which separates it from the nearest pulley; beyond this pulley theaction of the swivel is very limited, and is not instantaneous onvariations of load.

Among the solutions previously proposed to avoid at least partially thetwisting of the hoisting cable, there is yet another which is fairlycurrently used which consists purely and simply of increasing the deadweight of the block, which has however the drawback of reducing inconsequence the useful lifting load.

Hence means have not hitherto existed for enabling untwisting of thelifting cable in tower cranes with horizontal distributive jib to beeffectively overcome. This absence of means becomes more and moreunfavorable in proportion as the height of the crane increases, whichrenders practically impossible the provision of distributive tower jibcranes having very great heights, for example meters or more. In thecase of such heights, it is not in fact particularly possible to spreadout the vertical cables, that is to say the space a of FIGS. 1 and 2,proportionately to the hoisting height.

It is an object of the present invention to remedy these conditions.

It is a further object to provide a device for suspension anddisplacement of the load enabling elimination entirely of any tendencyof the load-carrying block to twist.

According to the invention there is provided the following combinationof devices: interposition of a swivel, or of a similar turning member,between the hook or the suspension crossbar of the load and the end ofthe hoisting cables, and association with the hoisting cables of amovable means bearing pulleys over which these cables pass and servingas a relay shifting in the reverse direction from the carriage andcompensating the theoretical displacement of ascent or of descent of thehoisting cable, resulting from translatory movement of the carriage, bya theoretical and equal movement of descent or of ascent of the samecable.

FIG. 3 shows, by way of purely of illustration and nonlimiting example,one embodiment of the device for suspension and displacement of theload, according to the invention.

l6a-16b designate the two strands of the hoist cable to which thecrossbar 17 is suspended by means of two swivels 18a-18, which suppressall tendency of the cable to twist, but which pose the problem of thehorizontal shifting of the hoisting carriage, without using the usualarrangement of cables for carriage shifting and for hoisting, referredto above with reference to FIG. 1, in which arrangement the shifting ofthe carriage is always accompanied by the descent of one of the strandsof the hoist cable and the equal ascent of the other strand of thiscable.

This problem is resolved by combining the suspension of the crossbar 17at swivels l8a-18b, with a system of compensation which forms part ofthe invention.

22 designates the tower of the crane, 23 its jib; 17 designates thehoist crossbar, 19a and 19b the two guide pulleys borne by the hoistcarriage 20. The winch for translation of the carriage is not shown;only the two ends of the cable 38 for translating the carriage arevisible, which ends are attached to the carriage.

The system comprises, for the hoisting of the load, two strictlysynchronized winch drums, 39a and 3% respectively, from which come twolifting cables l6a-16b. Each of the two cables ,16a-l6b passessuccessively over two guide pulleys, respectively 41a and 41b and42a-42b, before passing over the guide pulleys I9a-19b borne by thecarriage 20. The two guide pulleys 42a and 42b are borne at fixed pointsof the jib 23; but the pulleys 41a-4lb are borne by a movable apparatus43 which, according to the invention, is specifically essential toenable the hoisting hook to dwell at a constant level when the hoistingcarriage is shifted.

To raise or lower a load, it suffices to rotate the two drums 3.9a-39,simultaneously at the same speed, to obtain an equal ascent or equaldescent of the two cables 16a-l6b, the mobile apparatus or relay 43remaining motionless.

When the hoisting carriage 20 is to be shifted on the jib, bydisplacementof its cable 38 actuated by the winch not shown in thedrawing, the relay 43 compensates for the vertical displacement in thelevel of the hook 17 which would result therefrom.

Assuming in fact that the carriage 20 is shifted in the direction of thearrow 44, there results a displacement ofthe various strands of thecable 16b in the direction of the arrows 45a and 45b, with displacementof the relay 43 in the direction of the arrow 450, which causes finallya traction on the cable 16a, in the direction of the arrows 46a and 46b.The crossbar 17 thus dwells at a constant level.

It will be apparent that various changes and modifications may be madein the embodiment described without departing from the essential conceptof the invention as defined in scope by the appended claims.

lclaim:

l. A device for the suspension and displacement of the load in adistributive jib tower crane, said jib being transversed linearly by acarriage bearing hoist cables from which hang load-suspending means,said device comprising in combination, turning means interconnecting theloadsuspending means and the ends of the hoist cables, and a movablemeans bearing pulleys over which said hoist cables pass and serving as arelay for cooperatively shifting linearly in a direction reverse fromthat of the carriage and compensating for the theoretical displacementof ascent and descent of the hoist cables, resulting from thetranslatory movement of the carriage, by a theoretical movement equal tothe descent and ascent of the hoist cables.

2. A device according to claim 1, wherein said turning means is aswivel.

3. A device according to claim 1, wherein said loadsuspending meanscomprises a crossbar.

4. A device according to claim 1, wherein said loadsuspending meanscomprises a hook.

5. A device according to claim 3, wherein said loadsuspending meanscomprises a hook.

6. A device according to claim 1, wherein said turning means comprisetwo swivels attached to the ends of two hoist cables which pass over aplurality of guide pulleys including those of said movable means, to thedrums of two synchronized winches.

7. A device according to claim 6, wherein said loadsuspending meanscomprises a hook borne by a crossbar.

1. A device for the suspension and displacement of the load in adistributive jib tower crane, said jib being transversed linearly by acarriage bearing hoist cables from which hang loadsuspending means, saiddevice comprising in combination, turning means interconnecting theload-suspending means and the ends of the hoist cables, and a movablemeans bearing pulleys over which said hoist cables pass and serving as arelay for cooperatively shifting linearly in a direction reverse fromthat of the carriage and compensating for the theoretical displacementof ascent and descent of the hoist cables, resulting from thetranslatory movement of the carriage, by a theoretical movement equal tothe descent and ascent of the hoist cables.
 2. A device according toclaim 1, wherein said turning means is a swivel.
 3. A device accordingto claim 1, wherein said load-suspending means comprises a crossbar. 4.A device according to claim 1, wherein said load-suspending meanscomprises a hook.
 5. A device according to claim 3, wherein saidload-suspending means comprises a hook.
 6. A device according to claim1, wherein said turning means comprise two swivels attached to the endsof two hoist cables which pass over a plurality of guide pulleysincluding those of said movable means, to the drums of two synchronizedwinches.
 7. A device according to claim 6, wherein said load-suspendingmeans comprises a hook borne by a crossbar.